Midterm 1

Question 1

How would and evolutionary biologist define the term adaptation

Answer 1

an adaptation is any trait (structural, physiological, or behavioral) that enhances the reproductive success of an organism in its environment

Question 2

What three conditions are necessary and sufficient for the process of evolution by natural selection

Answer 2

1. Variation within the population
2. Inheritance being passed down to offspring
3. reproductive pressure within the population forcing the less fit to die off leaving the strong to reproduce

Question 3

Describe two different ways in which bacterial cells can exchange genes

Answer 3

1. cytoplasmic bridge formed between two bacterial cells, part or all of the DNA is passed from donor to recipient. DNA can be incorporated stably into the recipients chromosome
2. transformation: DNA leaks out of a dead bacterial cell and is taken up as free DNA by living cells and incorporated into their chromosome
3. transduction: a bacteriophage ‘accidentally’ packages up a part of the host (bacterial) chromosome instead of the viral genome. The bacteriophage can then inject the bacterial DNA into another bacterium, and the transferred DNA can be incorporated stably into the recipients bacterium’s chromosome

Question 4

Why do bacteria and fungi produce antibiotics

Answer 4

Antibiotics are produced as a means of competing with other micro-organisms for access to food resources

Question 5

Why do some scientists argue that we should not be using antibiotics in the production of livestock

Answer 5

70% of all antibiotics are given to livestock where the bacteria they are being used against can evolve to gain more resistance so when the antibiotics being used are needed in a life or death situation with a human, the bacteria is now resistant to our antibiotic attempts to subdue the infection

Question 6

What are the major ecosystem services that can be described as “provisioning” – i.e., things that humans harvest from ecosystems? Which of these services are currently increasing, and which are decreasing?

Answer 6

1. water- decreasing due to overexploitation
2. food - increasing, food production increasing
3. lumber - stable and sustainable
4. biofuels - increasing rapidly
5. genetic resources - decreasing due to extinctions

Question 7

Why is the land under I-5 in western Fresno County subsiding?

Answer 7

when water gets pumped out of aquafers underground faster than it can be replenished, it leads to land subsidence which can drop the levels of land by feet, somewhat rapidly

Question 8

Probiotics:

Answer 8

may be recommended after a course of antibiotics to aid in the re-colonization of the patient’s body by beneficial bacteria

Question 9

The USDA has recently approved the application of mixtures of viruses to prepared food products. Why? How can viruses be applied to food without risking human infection?

Answer 9

these viruses are bacteriophages which are harmless to humans but fight off infection with a similar result to antibiotics, however attack the bacteria like a virus attacking the human body

Question 10

Why might a commercial grape grower in Napa Valley consider native vegetation growing along creeks as providing an “ecosystem disservice”?

Answer 10

there are bugs near rivers that feed on grapevines that carry pierces disease, which is deadly to entire vineyards, leading to some farmers destroying all vegetation to prevent this

Question 11

What are some of the primary short-term threats to ecosystem services worldwide?

Answer 11

1. less fish stocks due to over fishing
2. degradation of water supply
3. climate change from increasing CO2 concentration
4. Pollution
5. Invasive Species
6. Species extinctions

Question 12

Define Biodiversity

Answer 12

all of the living organisms within all habitats earth make up the biodiversity

Question 13

Why might it be difficult to know whether or not an environmental perturbation has caused extinction and thereby reduce species-level biodiversity?

Answer 13

its very hard to tell if a species has gone extinct with certainty as well as much of the species on earth have not been discovered yet

Question 14

When measuring biodiversity, the diversity index D might be preferred over species richness because:

Answer 14

the D index incorporates the evenness of the different species’ abundances

Question 15

Which of the following is a key contributor to the current surge of extinction rates:

Answer 15

1. habitat destruction as native ecosystems are converted to agricultural production and as pollution degrades existing ecosystems
2. climate change
3. invasive alien species
4. over exploration of native species

Question 16

Ecologists are currently investing a great deal of research effort in understanding the relationship between biodiversity and ecosystem function. We can imagine at least three different types of underlying relationships:

Answer 16

1. which of these three scenarios (1, 2, 3) do you think represents the worst case scenario? explain your answer.
   
   1. worst is scenario 2 because at high biodiversity it is very unstable as any shift leads to a huge change in function
2. which is the best case scenario (that is, the scenario in which ecosystem function is least affected by biodiversity loss) explain your answer
   
   1. best is scenario 3 because it the ecosystem function is very stable with higher biodiversity
3. Which scenario is best supported by the experimental evidence that has been collected to date?
   
   1. scenario 3 is widely supported by experimental evidence

Question 17

You have been hired by the US Forest Service to implement a strategy for re-planting a Sierra Nevada forest that has been devastated by pathogens. You survey the forest, which is made up of five conifer species, each of which is roughly equally abundant, and find a series of approximately circular areas in which many trees are dead scattered through the forest. Within these “centers” of tree death, you find that three species of trees are still consistently healthy and alive, whereas the other two are dead

Answer 17

1. one of the big shots at the forest service recommends that you identify the two trees species that are dying and plant a large number of saplings of those two species to assist the regeneration of the forest in its original condition. Do you think this is a good plan? Explain your answer
   
   1. replanting trees will subject them to the pathogen that wiped out these species in the first place
2. Another of the big shots at the Forest Service recommends that you take one of the three tree species that is still healthy in each center and plant a large number of saplings of that healthy species in the “center” so that the forest will regenerate. Do you think this is a good plan? Explain your answer.
   
   1. also not a good plan because this will reduce the diversity of the forest making it less resistant to a pathogen as one pathogen can then wipe out a very large amount of the forest in one go
3. If YOU were the big shot at the forest service, what plan might you advocate
   
   1. replant a mixture of the tree that are alive, making it as diverse as possible

Question 18

Shown below are three graphs that relate the ‘intensity’ of some abiotic environmental condition to the performance of an organism experiencing that environmental condition. For each of the three graphs, give an example of an abiotic environmental condition that might produce such a graph. Explain your answers

Answer 18

a. anything that is not needed by the organism but become deadly in high amounts like toxicity or radiation (flat to slowly decreasing graph)
b. anything that is good in moderate amounts like temp, ph, macronutrients or major resources (graph with spike in middle)
c. anything that is a necessity like micronutrients (quick increase to then fall slowly at end)

Question 19

Define what ecologists mean when they talk about an organism’s “niche”

Answer 19

a niche is the set of conditions (environmental conditions and availabilities of key resources) that must be satisfied simultaneously to allow an organism to survive, grow and reproduce.

Question 20

Endotherms differ from ectotherms in that

Answer 20

metabolically-generated heat is the predominant source of warmth for endotherms

Question 21

As temperatures attain values that are much greater than those at which an organism performs optimally, the organism generally dies because

Answer 21

enzymes become denatured

Question 22

Explain how the structure of a protein ‘tunes’ that protein to function optimally at a particular temperature

Answer 22

enzymes are protein molecules that are folded into a 3 dimensional shape. Different bonds maintain the shape of a protein. Enzymes must maintain a proper shape, being flexible, but not enough to lose its shape. In hot environments there are more chemical bonds to keep the enzyme more rigid, thus being more resistant to heat. Opposite for cold

Question 23

What is the primary contributor to the human induced increase in CO2 concentration that has occurred over the past ca. 200 years

Answer 23

burning of coal and oil as the CO2 that is released is not recaptured fully

Question 24

How does CO2 in the atmosphere contribute to the warming of the planet

Answer 24

is allows UV light to enter from the sun, but as the heat from the earth is bounced back as infrared radiation, the CO2 does not allow it back out, trapping the heat inside

Question 25

Surface temps of the earth

Answer 25

are increasing currently more rapidly than they have in the known history of the earth

Question 26

Which of the follow is not a way in which organism are likely to respond to a warming environment

Answer 26

at a molecular level, evolving to produce enzyme molecules that are more flexible

Question 27

A resource for an organism could include

Answer 27

1. anything that can be consumed or used up by the organism, and that therefore could cause competition 2. energy rich compounds that are burned to drive the organism’s metabolism 3. atoms or simple molecules that are used as the basic building blocks for the molecules that are used to build the organism 4. nest sites, resting sites, or locations that provide refuges from enemies

Question 28

Which of the following is not essential resource for plants

Answer 28

amino acids

Question 29

Which of the following best describes the wavelengths of light that are most important in providing the energy for photosynthesis

Answer 29

visible light in the green wavelengths (500-600 nm)

Question 30

why might a plant that grows in both shady and sunny locations hold its leaves nearly vertically when it is growing in the sunniest location

Answer 30

doing this prevents all sunlight from entering the leaf which is to prevent photoinhibition, or too much sunlight then can be utilized for photosynthesis.

Question 31

Plants may experience a trade off between photosynthetic activity and their ability to harvest sufficient water for their needs because

Answer 31

the opening of the stomata needed to harvest CO2 also creates opportunities for water loss through transpiration

Question 32

When elongating plant roots that are exploring the soil for water or mineral resources encounter a valuable nutrient resource they may respond by

Answer 32

branching

Question 33

Macronutrients and micronutrients for plants differ primarily in

Answer 33

the amount needed for growth

Question 34

Let the total amount of light, water, CO2, and nitrogen harvested by a plant over its lifetime be lightTOT, waterTOT, CO2TOT, and NTOT respectively. Let the amount of light, water, CO2, and nitrogen required to make a single seed (= offspring) be written as lightSEED, waterSEED, CO2SEED, NSEED respectively

Answer 34

1. write an expression that applies Liebig’s law of minimum to plant fitness 1. fitness = min(lightTOT/lightSEED, waterTOT/waterSEED, CO2TOT/CO2SEED, NTOT/NSEED) 2. if CO2TOT/CO2SEED = 15, what is the minimum number of seeds that the plant could produce over its lifetime 1. 0 3. if CO2TOT/CO2SEED = 15, what is the max number of seed that the plant could produce over its lifetime 1. 15

Question 35

you census a population each year during the spring and consistently count approximately 1000 individuals. Then one year the census reveals that the population has doubled to reach 2000 individuals. what could have explained the change

Answer 35

1. an increase in the birth rate of the population 2. a decrease in the mortality rate within the population 3. an increase in immigration to the population 4. a decrease in the emigration rate from the population

Question 36

In organisms that reproduce by producing eggs, seeds, spores, etc. we typically see senescence in

Answer 36

the somatic cell lineages

Question 37

In organisms that reproduce exclusively by fission (e.g. some corals)

Answer 37

any cell could be passed on to future generations, and thus all cells have to be maintained without senescence

Question 38

Birds often produce clutch sizes smaller than the “Lack” clutch size (i.e. the clutch size that maximizes fitness returns from the current clutch) because

Answer 38

current reproduction trades off against future reproduction

Question 39

Explain how the presence of age-independent mortality factors (such as freezes, fires, and predation) can favor the evolution of senescence

Answer 39

to maintain cells without succumbing to senescence takes more energy than living with senescence, so if there was no threat to life besides time, it would make sense to spend that energy preventing senescence, but because there are external mortality factors, spending that energy actually shortens lifespan rather than succumbing to senescence

Question 40

A system with strong negative feedback is likely to respond to an experimental perturbation

Answer 40

by tending to move system back to its original equilibrium

Question 41

Scramble competition

Answer 41

involves an approximately equal sharing of resources among consumers, and therefore can have a strong influence on population growth rates

Question 42

Exactly compensating density dependence

Answer 42

1. is frequently produced by contest competition 2. occurs when the number of individuals surviving competition is constant across a range of high values of initial number of competitors

Question 43

does a mean density lower than the density of competition show that competition is not important

Answer 43

1. no competition will still likely happen just at lower amounts. Measuring the entire pond as the area for density can also be off in comparison to where the fish actually reside 2. measure density of fish near beds or food sources to see the density in those areas

Question 44

You are studying the incidence of cannibalism within a population of tadpoles. You find that the tadpoles are obligately cannibalistic: When two tadpoles meet, the larger one always eats the smaller one. Within a small pond, you place two tadpoles, and you measure the probability that they will encounter one another during a single day of their normal activity. Call this probability P

Answer 44

1. If you place one small tadpole in a pond with two larger tadpoles, what is the probability that it will die from cannibalism 1. (1-p) is the chance to survive from one large tadpole so two would be (1-p)^2, and the chance to die from cannibalism would be 1 - (1-p)^2 2. if you place one small tadpole in a pond with n larger tadpoles, what is the probability that it will die from cannibalism 1. 1 - (1-p)^n 3. Choose some value for p (whatever you wish) and then plot the relationship between the probability that the small tadpole dies from cannibalism versus the number of large tadpoles in the pond 4. Is cannibalism likely to be a density dependent source of mortality within the tadpole population 1. yes

Question 45

When a close population (i.e. no immigration or emigration) reaches it carrying capacity

Answer 45

the birth rate equals the death rate

Question 46

The logistic regression is written ΔN/Δt = rN(1 - N/K). For a population whos growth is described by this equation, what do we expect the per capita rate of population growth to be when the population size is very small relative to the carrying capacity

Answer 46

r

Question 47

When a constant number of immigrants colonizes a recipient population each year, and the recipients population size varies from year to year, this generates

Answer 47

density independent immigration for the recipients population

Question 48

Plato established a philosophy of essentialism which

Answer 48

proposed that the natural world contains a number of discrete and unchanging forms

Question 49

Studies by geologists in the 1700s and 1800s helped to establish that the earth was older than previously thought by showing

Answer 49

1. that sedimentation was gradual, but had produced very thick layers of rock 2. the erosion was gradual, but had produces very deep valleys

Question 50

Jean Baptiste de Lamarck made a contribution to developing a theory of evolution by

Answer 50

1. arguing that fossils forms could be linked through different sedimentary deposits, and leading to currently living forms 2. hypothesizing that evolution proceeded gradually over a very long time frame 3. suggested that changing environmental conditions could be a cause of evolutionary change 4. rejecting central aspects of the theory of essentialism

Question 51

Evolution by natural selection can produce organisms of tremendous complexity because

Answer 51

a blind process can produce adaptations which can accumulate over long periods of time

Question 52

Plato introduced the concept of the “great chain of being” (scala naturae) which suggests that

Answer 52

none of the above are true

Question 53

The study of fossils provided key observations that supported the first theories of evolution because

Answer 53

1. fossils were found of unknown presumably extinct animals showing the world is changing 2. deeper sedimentary strata contained mostly fossils of extinct animals 3. shallower sedimentary strata contained mostly fossils of animals that were similar or identical to animals still alive 4. the record of vertebrate fossils showed a sequence from fish to reptiles to birds to mammals in progressively shallower sedimentary deposits

Question 54

Which of the following is NOT a part of the theory of evolutions first proposed by Lamarck in 1800

Answer 54

all life forms present today descended from a single, unique appearance o life (”common descent”)

Question 55

In proposing their theory of evolution by natural selection, Darwin and Wallace

Answer 55

explained how evolution could occurs as an automatic process that could produce adaptation

Question 56

Darwin introduced a revolutionary concept, common descent. This concept suggest that

Answer 56

all organisms are derived from a single first appearance of life on earth

Question 57

What three conditions are necessary and sufficient for the process of evolution by natural selection to operate

Answer 57

1. variation within a population 2. inheritance of this variation from parent to offspring 3. pressure on reproduction allowing the fit to reproduce and unfit to die

Question 58

Some early views of the process of inheritance suggested that the relative contributions of the father to the traits expressed by their offspring might be greater than the relative contribution made by the mother. How was this view experimentally rejected

Answer 58

reciprocal crosses between different plant varieties, offspring were very similar showing they are both of equal or close to equal contribution

Question 59

An old and exceedingly grumpy catfish farmer grew tired of constantly being stabbed by the sharp spines in the fins of the catfish he raised in his ponds. One day he had an extremely brilliant idea that would not only save his own punctured hide but perhaps earn him a Nobel prize as well. He began to catch all the catfish in each pond, cut off all their sharp spines and release them otherwise unharmed back into the ponds. he supplemented their diet with fine catfish delicacies. He continued to do this to all of the spined progeny of the catfish in all of the ponds in the succeeding years. His goals were (1) to produce the first commercially available breed of spineless catfish and (2) drive the band-aid companies out of business

Answer 59

1. what proportion of the catfish population will be born spineless after 1 generation? 1. 0 2. What proportion of the catfish population will be born spineless after 10 generations 1. 0